Portable spot welder



Sept. 1953 A. o. BACKEN 2,651,701

PORTABLE SPOT WELDER Filed April 17, 1951 4 Sheets-Shet 1 IN VEN TOR.

Sept. 8, 1953 A. o. BACKEN PORTABLE SPOT WELDER 4 Sheets-Shut 3 Filed April 17, 1951 INVENTOR. d/i/zzzrdficza/a Sept. 8, 1953 A. o. BACKEN 2,651,701

PORTABLE SPOT WELDER Filed April 17, 1951 4 Sheets-Sheet 4 INVENTOR.

Patented Sept. 8, 1953 UNITED STATES PATENT OFFlCE PORTABLE SPOT WELDER Arthur Oliver Backen, Chicago, Ill.

Application April 17, 1951, Serial No. 221,393

3 Claims.

This invention relates generally to electric welders and it has particular relation to relatively small spot welders that are readily portable and can be lifted bodily and be manipulated by one hand of an operator.

Among the objects of this invention are: To provide a portable spot welder that will be simple and efiicient in operation and which can be readily and economically manufactured; to apply operating pressure to the work between the electrodes or jaws by relatively slight movement between the welder and an operating lever pivoted thereon; to energize the transformer of the welder by continued movement of the operating lever after predetermined pressure is applied to the work and for deenergizing it by reverse movement of the operating lever while pressure is still being applied to the work; to effect the energization by means of a switch operated by an over center toggle mechanism that, in turn is controlled by another toggle mechanism made up in part by the operating lever; to bring the energizin conductors into the rear end of the handle provided for carrying the welder; to bring the energizing conductors for the primary winding out of the forward end of the carrying handle; to provide a frame around the core of the transformer with the carrying handle integral therewith and with forwardly projecting ears on which the welding electrodes or jaws are mounted; to pivotally mount both of the electrodes or jaws and to provide for adjusting one of them to compensate for wear or erosion of the electrode tips; and to increase the heat radiating surfaces of the electrodes or jaws and the parts associated therewith.

Other objects of this invention will, in part, be obvious and in part appear hereinafter.

This invention is disclosed in the embodiments thereof shown in the accompanying drawings and it comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the constructions hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of this invention, reference may be had to the following detailed description, taken together with the accompanying drawings, in which:

Figure l is a view, partly in side elevation and partly in longitudinal section, of one embodiment of the invention;

Figure 2 is a top plan view of another embodi- 2 ment of the invention, the view here being a top plan view of the welder shown in Figure 3;

Figure 3 is a view, partly in side elevation and partly in section, illustrating another embodiment of the invention; 7

Figure 4 is a view, in side elevation, of the embodiment of the invention shown in Figures 2 and 3, the operating lever being illustrated in the retracted position with the electrodes or jaws separated for receiving work therebetween;

Figure 5 is a view, similar to the upper portion of Figure 3, and illustrating a modification of the manner in which the frame is secured to the core;

Figure 6 is a view, in side elevation, of the embodiment of the invention shown in Figure 5; and

Figure '7 is a view, partly in side elevation and partly in section, showing a modified form of electrode tip construction.

Referring now particularly to Figure l of the drawings, it will be observed that the reference character In designates, generally, a portable spot welder which includes a transformer that is indicated, generally, at II. The transformer l I includes a laminated core I2 which is made up of a stack of laminations suitably shaped as well understood by those skilled in the art. The laminated core I2 surrounds a primary winding 53 which has a relatively large number of turns and is arranged to be energized from an alternating current source having a voltage of the order of from 260 to 230 volts. The transformer II also includes a secondary winding I4. In the particular embodiment of the invention shown the secondary winding I 4 comprises a single turn of relatively large cross section conductor, such as a copper strap. The secondary winding M is arranged to operate at low voltage and to supply relatively high current through flexible conductor straps I5 and IE to welding electrodes or jaws that are shown generally at i! and [3. Each of the welding electrodes or jaws I l and I8 is made up of a jaw member I 9 and 29, respectively, which have welding tips 2! and 22 at their outer ends extending at right angles toward each other. Preferably the jaw members i9 and 20 are formed of good conducting material such as round copper rods. As shown in the drawing the welding tips 2| and 22 are arranged to engage the opposite sides of sheet metal strips 23 and 24, which constitute the work, for welding them together by passage of relatively heavy current therethrough. It will be understood that other shapes and forms 3 of work can be welded, the strips 23 and 24 being shown for illustrative purposes only.

Each of the jaw members l9 and 29 is carried by a support bracket 2i? and 28, respectively, which are pivoted at 29 and 530 between ears, one of which is shown at 3!, which form a part of a frame, shown generally at 32, for carrying the transformer ll. Between the ears 3i there are provided cross members 33 and 35 which are integral therewith and which bear against the adjacent end of the stack of laminations forming the core 52. Bolts 55 and 36 extend through the cross members 33 and 34 and are provided for the purpose of interconnecting the flexible conductor straps i5 and it to the respective ends of the U-shaped single turn secondary winding 53. Strips of insulation 37 and 38 underlie the flexible conductor strap i5 and bracket 29 for the purpose of insulating them and the associated parts from the frame 52. served that the support bracket 28 is carried by a support member 39 which is pivoted at 39 between the ears st of the frame 32. In order to compensate for wear of the weldingtips 2! and 22 it is desirable to provide for adjusting the position of one of the welding jaws H or it. For this purpose provision is made for adjusting the position of the welding electrode or jaw Hi. This is accomplished by an adjusting screw 46 which is threaded through a bracket 4! that is integral with the cross member 34 forming a part of the frame 52. The end of the adjusting screw 49 bears against the underside of the support member 39, and on rotation of the adjusting screw 45, it is understood that the position of the welding electrode or jaw i3 is changed with respect to the position of the welding electrode or jaw llv With a view to securely mounting the transformer ii on the frame 32 and for holding the laminations of the core l2 together as a single unit, through bolts 44 are provided. It will be observed that the bolts 44 extend through an end cap 45 which is located at the left hand end of the laminated core 52. extend through the laminated core i2 and are threaded at 4% into the adjacent portion of the ears 3i.

It will be observed that the end cap 45 has a neck 4? formed integrally therewith and that it extends upwardly. Conductors 48 and 49 are located in the neck 4? and they are provided for energizing the primary winding H3. The manner in which the current flow through the conductors 48 and 49 is controlled will be described presently,

The portable spot welder it is carried by a handle 5b which is formed integrally with the frame 32 and has a generally U-shaped cross section. There is a depending projection 5! from the underside of the handle 59. This is for the purpose of facilitating the grasping of the handle with the projection 5| located between the first and second fingers. It will be noted that the handle 55 extends along the entire length of the core l2 and that it overlies at 52 the upper end of the neck ll. If desired the upper end of the neck 4'! can be joined integrally with the rear end of the handle 55.

Pivoted at 53 near the rear end of the handle 5% is an operating lever 54. It will be noted that the operating lever 5d is generally U-shaped in cross section and is inverted so that it generally overlies the upwardly opening U-shaped handle 55 and encloses a cavity therebetween. A coil It will be ob L As shown they all spring 55 extends around the pivot 53 and acts to bias the operating lever 54 in a counterclockwise direction.

The operating lever 54 is employed for effecting relative movement between the welding electrodes or jaws ii and 18. This is accomplished by pivoting at 56 on the operating lever 54 a conecting link 51 which is pivoted at its other end at 58 on an arm 21 which is formed integrally with and extends from the support bracket 21. The lever 54, link 5'! and the pivot 56 associated therewith constitute a toggle which is arranged so as to approach the center position that is indicated by the broken line 59 which extends through the pivots 53 and 58. However, the arrangement is such that the forward end of the operating lever 54 engages the frame 32 at 54' so as to prevent the toggle thus formed from going past the position represented by the broken line 59. As a matter of fact it approaches this position but is prevented from reaching it. It will be noted that the pressure for moving the welding electrode or jaw H to engage the work represented by the strips 23 and Z4 is ap plied to the operating lever 54 generally at a position above the pivot 56. With this arrangement it is possible to apply a tremendous force to move the weldin electrodes or jaws i1 and it relatively toward each other merely by the grasping of the handle 55 and the operating lever 54 about the pivot 55 and moving them toward each other to the position shown in Figure l.

The current flow to the primary winding l3 through the conductors 48 and 49 is controlled by contacts 55 and 6!. It will be observed that these contacts are carried by a stationary insulating support 82 and a movable insulating support 63, respectively, which are located near the rear end of the U-shaped handle 50. The contacts 6t and M are connected in the conductor 59 so that, when they are in engagement, the circuit is completed for energizing the primary winding E3 of the transformer II, assuming of course that the conductors 48 and 49 are connected suitably to a source of alternating current of the required voltage and current supplying capacity.

In accordance with conventional practice the conductors 48 and 49 are enclosed in a sleeve of insulation to form a cable that is indicated at 64 and this cable extends through a sleeve 65 that is formed integrally with the handle 50 at its rear end.

The contacts 50 and 51 are arranged to be operated with a snap action for closing and opening. For this purpose the movable insulating support 53 is carried by an arm 56 which is pivoted at 61 on the U-shaped handle 50. A coil tension spring 58 interconnects the arm 66 and a lever 69 which also is pivoted on the handle 59 at 15. The lever 69 is biased in a counterclockwise direction by a coil compression spring "H. The lever 69 is operated on movement of the link 51 through the agency of an adjusting screw 12 which projects through the link 5? as shown and engages the lever 69 at a position slightly at the right of its pivot Hi.

When the operating lever 54 is released to relieve the pressure on the welding electrodes or jaws H and E8, the movement of the link 51 is extremely slight so that in effect the pressure is maintained on the work being welded such as the strips 23 and 24. However, a slight movement of the link 51 in the releasing direction permits the spring H to swing the lever 69 in a counterclockwise direction so that the point 14 where the coil tension spring 68 is connected to the lever 69 swings past the line joining the pivots 61 and I0 as represented by the broken line I3. As soon as the point I4 moves past the broken line 13, the coil tension spring 68 is effective to snap the arm 66, movable insulating support 63 and the contact 6I carried thereby to the open position. As a result, the contact 6| separates from the stationary contact 60 with a snap action and the primary winding I3 is immediately deenergized.

The continued movement of the operating lever 54 in a counterclockwise direction, as urged by the spring 55, then is effective to release the pressure applied to the work between the welding electrodes or jaws IT and I8.

When the operating lever 54 is moved to cause the welding electrodes or jaws I! and I8 to engage the work between the welding tips 2I and 22, initially no movement of the movable contact El takes place. Rather the movement of the operating lever 54 continues until substantial pressure is applied to the work between the welding tips 2I and 22. Then during the final movement of the operating lever 54, the adjusting screw 12 engages the lever 69 and swings it in a clockwise direction so that the point I4 at the connection of the spring 68 thereto moves above the broken line I3. At this time the contact EI moves into engagement with the stationary contact 60 with a snap action and, as a result, the primary winding I3 of the transformer II is energized. In this manner the welding pressure first is applied to the work and then the circuit for energizing the welding transformer is automatically completed. Likewise, on release of operating pressure from the operating lever 54, welding current first is cut off and operating pressure can be maintained on the work as long as is desired. Subsequently on release of the operating lever 54, the spring 55 serves to swing it in a counterclockwise direction in a position where welding tips 2I and 22 no longer engage the work. The work then can be removed or the welding tips 2I and 22 can be moved to another position for making another weld on the work.

Referring now particularly to Figures 2, 3, and 4 of the drawings, it will be observed that the reference character 80 designates, generally, another embodiment constructed in accordance with this invention. The portable spot welder 80 includes a transformer, shown generally at 8|, which is generally the same as the transformer II referred to hereinbefore. The transformer 8I includes a laminated core 82 enclosing a primary winding 83 and a single turn secondary winding 84. Flexible conductor straps 85 and 86 are employed for interconnecting the terminals of the secondary winding 84 to welding electrodes or jaws 81 and 83 respectively. As before, each of the welding electrodes or jaws 81 and 88 includes a jaw member 89 and 90 that preferably is formed of good conducting material such as round copper rod. Also they include welding tips 9| and 92 extending at right angles to the jaw members 89 and 90, respectively, engaging sheet metal strips 93 and 94, constituting the work, for welding them together. It will be understood as indicated before, that other shapes and sizes of work can be employed in using the portable spot welder 80.

Each of the welding electrodes or jaws 81 and 88 includes a support bracket 91 and 98, respectively, and they are provided with radiating fins 9'1 and 98 for increasing the surface area thereof and promoting cooling of the associated parts. This cooling action is important when it is appreciated that on continuous use of the portable spot Welder 80, considerable heat is generated by current flowing through the welding electrodes or jaws 81 and 88 which must be dissipated in some manner. By providing the radiating fins 91' and 98 the cooling effect of the atmosphere is increased. The support brackets 91 and 98 are pivoted at 99 and I90, respectively, between ears IOI which, as shown more clearly in Figure 2, are formed integrally with a frame that is designated generally by the reference character I 8-2. The frame I 92 has a central section I03 which is generally rectangular in cross section and has a rectangular opening for receiving the laminated core 82 of the transformer 8|. The frame I92 is provided for carrying the transformer 8| and the central section I03 is arranged to be slipped over the laminated core 82.

The frame I02 is held in position on the laminated core 82 at the forward end by means of transversely extending bars I04 into which bolts Hi5 are threaded. It will be observed that the bolts I05 extend from and through an end cap I 96 at the rear end of the laminated core 82. The laminations of the core 82 are themselves clamped by means of bolts II). which extend through the corners thereof with the heads I08 at the forward end and nuts I09 at the rear end underneath the cap I96. As shown more clearly in Figure 3 of the drawings the bars I04 are offset as indicated at I I 53 for the purpose of clearing the heads I98 of the bolts I01. The central section I 93 of the frame I02 is clamped between the ends of the transverse bars I04 and the end cap I 08. In this manner the frame I02 is securely fastened relative to the transformer 8I.

It will be observed in Figure 3 of the drawings that a spacer III is interposed between the ends of the single turn secondary winding 84. Bolts I I2 extend through the flexible conductor straps and 85 and the respective ends of the single turn secondary winding 84 into the spacer III. As shown, the lower bolt I I2 is suitably insulated from the spacer III.

With a View to adjusting the position of the welding electrode or jaw 88 with respect to the other welding electrode or jaw 87, there is provided an adjusting screw I I 4 which is threaded in a bracket I I5, spaced by a layer of insulation I I 6, from the support bracket 98. It will be observed that the adjusting screw H4 at its forward end bears against a boss I I3 which is formed integrally with the frame I 02 on the underside of its central section I03.

Formed integrally with the frame Hi2 and extending above the central section I93 thereof is a handle Hi. It will be noted that the handle II"! has depending projections H8 on the underside. They are for the purpose of facilitating the gripping of the handle II I by the hand of the operator. The handle II'I has a U- shaped cross section H9 and at its rear end there is pivoted at I29 an operating lever I2I. The operating lever I 2! is generally U-shaped in construction and it fits over the U-shaped cross section IIQ of the handle II! and generally encloses the mechanism therein. A coil spring I22 acts around the pivot I26 for biasing the operating lever I 2! in a counterclockwise direction.

The operating lever I2I constitutes a part of a toggle mechanism that is employed for moving the welding electrodes or jaws 81 and 88 relative Pivoted at Mt intermediate the ends of the operating lever l2i and near the forward end thereof is a link i2 5. At its other end the link 213 is pivoted at E25 to an arm 62% which is formed "l to each other.

integrally with the support bracket :2 that carries the jaw member 89.

The primary winding 83 of the transformer 85 is energized through conductors i2? and IE8. It will be noted that these conductors extend through a sleeve 529 that is formed integrally with the handle ill at its rear end. In accordance with conventional practice the conductors i2? and are formed in a cable 635 and it is arranged to be connected to a suitable source of alternating current such as a source operating at a'voltage ranging from 200 to 239 volts as will be understood.

With a view to energizing the primary winding S3 of the transformer 8! at will, contacts are interposed. in the conductor iE'l. For this purpose a stationary contact lii and a movable contact E32 are provided. As shown in Figure 3 the contact iiil is carried by a stationary insulating support E33 while the contact 522 is carried by a movable insulating support its. The movable insulating support ESQ in turn is carried by an 'arm H35 which is pivoted at i35 on the U-shaped cross section H9 of the handle ill. in order to operate the contact ltZ with a snap action into and out of engagement with the stationary con tact Edi, a coil tension spring it? is employed. As shown the coil tension spring i3? is connected at one end to the arm i3 and is connected. at the other end at i238 at one end of a lever 53%. The lever 4259 is pivoted at Me on section lie of the handle ill and a spring Mi is employed for urging the lever it in a counterclockwise direction. Ihe lever B39 arranged to be operated by means of an adjusting screw M2 that is carried by the operating lever lili. I [in insulating barrier M3 is secured by a screw Hit to the bottom of the U-shaped cross section of the handle ill for the purpose of insulating more fully the parts associated with the movable contact l32.

In the construction shown in Figures 3 and 5 of the drawings, the end cap M36 is separate from the handle i ll. It will be understood that, if desired, the end cap We can be secured to the handle i ii.

In operation, the work represented by the strips 93 and 9 s positioned between the welding tips 95 and s2. Ordinarily this will be ac ccmplished by bringing the portable spot welder 2i? into the welding position. Then the operating lever iili is moved from its position shown in Figure e of the drawings in a clockwise direction to actuate the welding electrode or jaw Bl downwardly for engaging the work. This is acoomplished through the link Hill which forms a part of the toggle linkage that also includes the operating lever IN. The arrangement of the operating lever I26 with respect to the handle ill is such that the toggle cannot go past the center position represented by the broken line M5 in Figure 3 extending through the pivots Hit and 525. However, the construction is such that thi position is closely approached. Under these circumstances it is possible to apply a relatively great force to the Work between the welding electrodes or jaws ill and 88 on application of pressure to the operating lever lZl by the operator. It will be observed that this pressure is applied generally along a line through the pivot M3.

the U-shaped cross After the work has been engaged by the welding tips 9! and 92 and sufficient pressure has been applied thereto, the adjusting screw [d2 engages the right end of the lever l39 and swings it in a clockwise direction. As the left end of the lever its passes beyond the broken line MB which interconnects the pivot I36 and the pivot lilo, the contact It is moved with a snap action into engagement with the stationary contact ESE. The circuit is then completed for energizing the primary winding 83 of the transformer 8i and current flows through the secondary winding 8d and between the welding tips 9| and S2 for performing the welding operation.

After suni ient current has flowed to perform the welding operation in the judgment of the operator, he releases the pressure slightly on the operating lever i2l. This slight movement of the operating lever l2! which results is insufficient to remove pressure from the work but is sufficient to permit the spring Ml to shift the lever its downwardly past the broken line 146. Thereupon the spring lfil is effective to move the contact 832 with a snap action out of engagement with the stationary contact lSl. Thereupon the ficw of current to the transformer 3| ceases and current no longer flows between the welding tips ti e2. However the pressure can be applied to the work as long as is desired. Thereafter the operating pressure is removed from the operating lever liil and it is swung in a counterclockwise direction to the open position shown in Figure 4 by the spring I22.

construction shown in Figures 5 and 6 of the drawings is generally similar to that illustrated in Figures 2, 3 and i and just described. However, the manner in which the laminated core is secured in position on the frame IE2 is somewhat different. It will be observed in Figure 5 that bosses Mil are formed integrally with the ears ltl which project forwardly from the transformer 8i. Through bolts M9 extend from the cap lllt through the corners of the larninations of the core 32 into these threaded bosses i 23. With this construction then it is unnecessary to employ the transverse bars Hi4 and the centrally located bolts as shown in Figure 3.

Also it will be noted in Figure 5 that the conductors Hi and E28 are located in a groove I) in the forward end of the handle I l. and therefore are connected to the primary winding 83 of the transformer 8! at the forward rather than at the rear end as in Figure 3.

In Figure 6 of the drawings radiating fins [SI and i525 are illustrated as extending from the jaw members 89 and 90. They assist further in cooling the associated parts and together with the fins til and 92? provide an increased radiating surface for the welding electrodes or jaws 81 and 88.

In Figure '7 of the drawings a modified welding tip construction is illustrated. A relatively small diameter shank ltd extends transversely through the jaw member 89 and is threaded and tapered at its lower end lfii for interfitting with a relatively large diameter welding tip I62. This con struction makes it possible to use a relatively short length of copper rod of large diameter, for example 1 inch long by inch diameter, for the welding tip and a relatively longer shank I of copper rod of small diameter, for example /8 inches lo g by /8 inch diameter. A set screw I63 threaded into the end of the jaw mem- 9 her 89 acts to hold the shank I60 and the welding tip I62 carried thereby in position.

Since certain further changes can be made in the foregoin construction and difierent embodiments of the invention can be made without departing from the spirit and scope thereof, it is intended that all matter shown in the accompanying drawings and described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

1. A portable manually operable spot welder comprising, in combination, a transformer having a core formed by a stack of laminations of magnetic material with primary and secondary windings extending therethrough, frame means secured to said core, a pair of welding jaws connected for energization to said secondary winding and carried by said frame means and mounted for movement toward and away from each other to engage work therebetween, an operating lever pivoted on said frame means, a link interconnecting said lever and one of said jaws and therewith forming a toggle joint arranged to be substantially extended when said jaws engage the work, switch means carried by said frame means for connecting said primary winding to a source of alternating current and including a pivotally mounted contact member and a cooperating contact member, a control lever pivoted intermediate its ends on said frame means with one end arranged to swing past the pivot axis of said pivotally mounted contact member and the other end operatively connected to said operating lever, a coil tension spring interconnecting said one end of said control lever and said pivotally mounted contact member for shifting the same with a snap action into and out of engagement with said cooperating contact member on swinging movement of said control lever, and a spring cooperating with said control lever to bias the same to swing in a direction opposite to that in which it is swung by said operating lever.

2. A portable manually operable spot welder comprising, in combination, a transformer havin a core formed by a stack of laminations of magnetic material with primary and secondary windings extending therethrough, frame means secured to said core including a carrying handle extending therealong, a pair of welding jaws connected for energization to said secondary winding and carried by said frame means and mounted for movement toward and away from each other to engage work therebetween, an operating lever pivoted on said handle, a link interconneeting said lever and one of said jaws and therewith forming a toggle joint arranged to be substantially extended when said jaws engage the work, switch means carried by said handle for connecting said primary winding to a source of alternating current and including a pivotally mounted contact member and a cooperating contact member, a control lever pivoted intermediate its ends on said handle with one end arranged to swing past the pivot axis of said pivotally mounted contact member and the other end operatively connected to said operating lever, a coil tension sprin interconnecting said one end of said control lever and said pivotally mounted contact member for shifting the same with a snap action into and out of engagement with said cooperating contact member on swinging movement of said control lever, and a spring cooperating with said control lever to bias the same to swing in a direction opposite to that in which it is swung by said operating lever.

3. A portable manually operable spot welder comprising, in combination, a transformer having a core formed by a stack of laminations of magnetic material with primary and secondary wind ings extending therethrough, frame means secured to said core, a pair of welding jaws connected for energization to said secondary winding and carried by said frame means and mounted for movement toward and away from each other to engage work therebetween, an operating lever pivoted on said frame means, a link interconnecting said lever and one of said jaws and therewith forming a toggle joint arranged to be substantially extended when said jaws engage the work, switch means carried by said frame means for connecting said primary winding to a source of alternating current and including a pivotally mounted contact member and a cooperating contact member, a control lever pivoted on said frame and arranged to be operated by said operating lever when the same is swung to move said welding jaws into and out of engagement with the work, and spring means operatively interconnecting said control lever and said pivotally mounted contact member for shifting the same with a snap action into and out of engagement with said cooperating contact member on swinging movement of said control lever, and a spring cooperating with said control lever to bias the same to swin in a direction opposite to that in which it is swung by said operating lever.

ARTHUR OLIVER BACKEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 222,787 Hurlbut Dec. 23, 1879 1,489,458 Petersen Apr. 8, 1924 2,418,781 Lewis Apr. 8, 1947 2,440,463 Cornwall Apr. 27, 1948 2,454,338 Pityo Nov. 23, 1948 2,464,054 Panik Mar. 8, 1949 2,465,879 Kauder ll/Iar. 29, 1949 2,470,074 Manning May 10, 1949 2,517,653 Gaston Aug. 8, 1950 2,535,946 Mulder Dec. 26, 1950 

